Rogue Valley Microdevices deposits undoped polysilicon on silicon wafers using low pressure chemical vapor deposition (LPCVD). Our LPCVD polysilicon films deliver the uniformity, conformal coverage, and stable mechanical properties that structural MEMS components, surface micromachining, and semiconductor device fabrication demand. Why Choose Rogue Valley Microdevices for Undoped Polysilicon Film Property Control: LPCVD polysilicon with control over crystallinity, uniformity, grain size, and film stress Full Stack In-House: Polysilicon integrates directly with thermal oxide, nitride, and metal layers, with no multi-vendor shipping between films Two Qualified Recipes: Standard (620°C) and low-temperature (580°C) undoped polysilicon options Broad Wafer Support: Customer-supplied wafers welcome, from 50.8mm to 200mm Prototype Through Production: Prototype-friendly engagement backed by our MEMS foundry for scale-up LPCVD Polysilicon Deposition Process LPCVD polysilicon is deposited when silane (SiH₄) decomposes into silicon and hydrogen at temperatures of 580°C and above inside a controlled furnace environment. The reaction forms a uniform polysilicon layer across the silicon wafer surface, which is why engineers rely on LPCVD polysilicon deposition for structural and electrical layers in MEMS devices and semiconductor technologies. LPCVD polysilicon offers several advantages for MEMS fabrication: - Excellent film uniformity across silicon wafers - Strong adhesion to silicon substrates - Good conformal coverage over microstructures - Stable mechanical properties for MEMS devices - High compatibility with semiconductor process flows LPCVD Polysilicon Film Options We offer two undoped polysilicon films, both deposited in our production furnaces: Standard undoped LPCVD polysilicon: Process Temperature 620°C; Maximum Thickness Up to 1µm; Film Character Polycrystalline as deposited; Typical Use Structural beams, electrostatic actuators, resonators, diaphragms Low-temperature undoped LPCVD polysilicon: Process Temperature 580°C; Maximum Thickness Up to 3µm; Film Character Near-amorphous as deposited, with finer surface morphology; Typical Use Sacrificial layers and thicker structural films for surface micromachining Both films deposit with compressive as-deposited stress, with stress data available for your design work. Our engineers help you select the recipe and thickness that match your structural or sacrificial requirements. Supported Wafer Sizes and Materials LPCVD polysilicon deposition is available on 50.8mm, 76.2mm, 100mm, 125mm, 150mm, and 200mm wafers. Supported substrate materials include: - Silicon - Silicon on insulator (SOI) - Quartz and sapphire (quoted individually; compatibility confirmed per process) - Other specialty materials by request Polysilicon as a Structural Material for MEMS Polysilicon is one of the most widely used structural materials in MEMS devices. Because it combines semiconductor compatibility with mechanical strength, it lets engineers integrate sensing, mechanical movement, and electrical functionality within a single device structure. Structural polysilicon supports devices such as: - Pressure sensors - Accelerometers - Resonators - Electrostatic actuators - Micro-mechanical beams and diaphragms Sacrificial Polysilicon for Surface Micromachining Engineers frequently use undoped polysilicon as a sacrificial layer in MEMS surface micromachining. During fabrication, the polysilicon layer supports structural films like silicon nitride, silicon dioxide, or PVD metal layers while device features form above it. Once the structural layers are complete, the sacrificial polysilicon is removed to release suspended MEMS components. Many MEMS processes pair polysilicon sacrificial layers with xenon difluoride (XeF₂) vapor etching for the final release step. XeF₂ selectively etches silicon and polysilicon while leaving many structural films largely unaffected, and the volatile byproducts simply exit the chamber. Because this vapor-phase release eliminates liquid surface tension, it helps prevent stiction in delicate MEMS structures. Surface micromachining with multiple polysilicon layers separated by sacrificial oxide films enables suspended micro-mechanical beams, micro-springs and resonators, electrostatic actuators, and complex MEMS architectures, all built directly on silicon wafers. Deposit, pattern, release. Polysilicon goes down over a sacrificial oxide (1), is patterned into the device shape (2), and the oxide beneath is etched away (3), leaving a free-standing structure anchored to the wafer — the basis of beams, micro-springs, resonators, and actuators. Undoped Polysilicon Deposition Integrated with Full Wafer Services Polysilicon deposition is one part of our broader wafer services and MEMS foundry capabilities. Similar to our LPCVD silicon nitride, these films come out of production furnaces with consistent thickness and strong across-wafer uniformity. Our engineering team works closely with you to integrate polysilicon layers with complementary thin-film deposition processes and micromachining steps. By combining LPCVD polysilicon deposition with foundry services like photolithography, wet etch, and DRIE silicon etch, we help innovators build reliable, high-performance devices on silicon wafers. Engineers also value undoped polysilicon because it keeps process options open: the film gains useful electrical properties when doped later, and it patterns cleanly on the same dry etch and DRIE lines that will shape the rest of your device, so a film started here can carry through the whole flow without changing vendors. From Prototype to Production Whether you need a few development wafers or a recurring production supply, the same furnaces and the same recipes run your film. That consistency is why customers treat our fab as an extension of their own engineering team. If you are still defining the device, our MEMS design services group can help you choose between structural and sacrificial polysilicon strategies before you commit to a flow. Request a Quote for LPCVD Polysilicon Deposition Tell us your thickness target, wafer size, and how the polysilicon fits your device, structural, sacrificial, or both, and our engineers will respond with a practical process recommendation. Request a quote to get started, or browse our ready-to-ship wafer inventory if you need film-coated wafers now.
